Scheme for Managing Last-Modified Information

1. A method comprising: generating, by a computing device and based on a first update, an updated version of a resource; determining, based on an actual update time of the updated version of the resource: a first approximate update time that is before the actual update time; and a second approximate update time that is after the actual update time; determining a time window based on the first approximate update time and the second approximate update time; receiving, from a client device, a request for the resource; determining, based on whether the request was received within the time window, one of the first approximate update time or the second approximate update time; and sending, to the client device and in response to the request for the resource: the determined one of the first approximate update time or the second approximate update time; and the updated version of the resource.

2. The method of claim 1 , further comprising: in response to a request from a first device, sending the updated version and an indication that the updated version was last updated at the first approximate update time; and in response to a request from a second device, sending the updated version and an indication that the updated version was last updated at the second approximate update time.

3. The method of claim 1 , wherein the determining one of the first approximate update time or the second approximate update time comprises: determining the first approximate update time in response to determining that the request was received within the time window.

4. The method of claim 1 , further comprising: generating the first approximate update time by rounding down the actual update time; and generating the second approximate update time by rounding up the actual update time.

5. The method of claim 1 , further comprising: receiving, from the client device, a validation request comprising the first approximate update time; and in response to determining that the validation request was received outside of the time window, determining whether the first approximate update time of the validation request is less than or equal to the actual update time.

6. The method of claim 5 , further comprising: in response to determining that the first approximate update time of the validation request is less than or equal to the actual update time, sending, to the client device, the second approximate update time and the updated version of the resource.

7. The method of claim 1 , further comprising: receiving, from the client device, a validation request comprising the second approximate update time; in response to determining that the validation request was received outside of the time window, determining whether the second approximate update time of the validation request is less than or equal to the actual update time; and in response to determining that the second approximate update time is greater than the actual update time, sending, to the client device, a response indicating that the updated version of the resource has not been further updated.

8. A method comprising: determining, by a computing device, an actual update time of an updated version of a resource; determining, based on the actual update time of the updated version of the resource: a first approximate update time that is before the actual update time; and a second approximate update time that is after the actual update time; determining a time window based on the first approximate update time and the second approximate update time; receiving, by the computing device and from a client device, a validation request for the resource, wherein the validation request comprises a timestamp associated with a version of the resource at the client device; determining, based on a determination of whether the validation request was received outside of the time window, whether to use the timestamp in generating a response to the validation request; and sending, to the client device, the response to the validation request.

9. The method of claim 8 , wherein the determining whether to use the timestamp in generating a response to the validation request comprises: comparing, based on a determination that the validation request was received outside of the time window, the timestamp with the actual update time.

10. The method of claim 8 , further comprising: in response to determining that the validation request was received within the time window, sending, to the client device in response to the validation request, the first approximate update time.

11. The method of claim 8 , further comprising: in response to determining that the validation request was received outside of the time window, determining whether the timestamp is less than or equal to the actual update time; and determining, based on a determination of whether the timestamp is less than or equal to the actual update time, whether to send the second approximate update time.

12. The method of claim 11 , further comprising: in response to determining that the timestamp is greater than the actual update time, sending, to the client device, the response comprising an indication that a cached resource at the client device is up-to-date.

13. The method of claim 8 , further comprising: receiving a different updated version of the resource; updating, based on the different updated version and at a different update time outside of the time window, the resource; and determining a different time window based on the different update time.

14. The method of claim 8 , further comprising: receiving, by the computing device and from the client device, a read request for the resource; sending, to the client device and based on whether the read request was received within the time window, one of the first approximate update time or the second approximate update time.

15. An apparatus comprising: one or more processors; and memory storing computer-executable instructions that, when executed by the one or more processors, cause the apparatus to: generate, based on a first update, an updated version of a resource; determine, based on an actual update time of the updated version of the resource: a first approximate update time that is before the actual update time; and a second approximate update time that is after the actual update time; determine a time window based on the first approximate update time and the second approximate update time; receive, from a client device, a request for the resource; determine, based on whether the request was received within the time window, one of the first approximate update time or the second approximate update time; and send, to the client device and in response to the request for the resource: the determined one of the first approximate update time or the second approximate update time; and the updated version of the resource.

16. The apparatus of claim 15 , wherein the instructions, when executed by the one or more processors, further cause the apparatus to: in response to a request from a first device, send the updated version and an indication that the updated version was last updated at the first approximate update time; and in response to a request from a second device, send the updated version and an indication that the updated version was last updated at the second approximate update time.

17. The apparatus of claim 15 , wherein the instructions, when executed by the one or more processors, further cause the apparatus to: determine the first approximate update time in response to determining that the request was received within the time window.

18. The apparatus of claim 15 , wherein the instructions, when executed by the one or more processors, further cause the apparatus to: receive, from the client device, a validation request comprising the first approximate update time; and in response to determining that the validation request was received within the time window, send, to the client device, the first approximate update time in a Last-Modified field.

19. The apparatus of claim 15 , wherein the instructions, when executed by the one or more processors, further cause the apparatus to: receive, from the client device, a validation request comprising the first approximate update time; and in response to determining that the validation request was received outside of the time window, parse the first approximate update time from an If-Modified-Since field of the validation request; and compare the parsed first approximate update time with the actual update time; and send, to the client device and based on the comparison, the second approximate update time.